Electronically controlled antenna system

ABSTRACT

IN A TACAN BEACON ANTENNA, A MONOPOLE RADIATOR SURROUNDED BY TWO OR MORE CONCENTIC CIRCULAR ARRAYS OF PARASITIC ELEMENTS, WHICH ELEMENTS ARE DIGITALLY INHIBITED IN SEQUENCE IN A PREDETERMINED MANNER, IS USED TO PRODUCE A ROTATING RADIATION PATTERN CAPABLE OF PRODUCING 15 AND 135 CYCLE-PER-SECOND SIGNALS AT A RECEIVER. PARASITIC ELEMENTS ARE INHIBITED BY BEING OPEN CIRCUITED BY DIGITALLY CONTROLLED SWITCHING DIODES. RECIRCULATING SHIFT REGISTERS ARE USED TO INHIBIT PARASITIC ELEMENTS IN THE CIRCULAR ARRAYS TO PRODUCE THE REQUIRED MODULATION RADIATION PATTERN. A COMMON CLOCK IS USED TO STEP SAID REGISTER ALONG TO PRODUCE THE DESIRED ROTATING PATTERN.

Feb. 2, i971 l.. HIMMEL ETAL 3,560,973

ELECTRONICALLY CONTROLLED ANTENNA SYSTEM Filed Nov. l, 1968 2 Sheets-Sheet 1 /ATTORNEY mu @X95 0m Q qos SQQQW;

3,560,978 Patented Feb. 2, 1971 3,560,978 ELECTRONICALLY CONTROLLED ANTENNA SYSTEM Leon Himmel, Upper Montclair, Sven H. Dodington,

Mountain Lakes, and Ernest G. Parker, Convent Station, NJ., assignors to International Telephone and Telegraph Corporation, Nutley, NJ., a corporation of Delaware Filed Nov. 1, 1968, Ser. No. 772,686 Int. Cl. G01s 1/48 U.S. Cl. 343-106 3 Claims ABSTRACT F THE DISCLOSURE In a TACAN beacon antenna, a monopole radiator surrounded by two or more concentric circular arrays of parasitic elements, which elements are digitally inhibited in sequence in a predetermined manner, is used to produce a rotating radiation pattern capable of producing and 135 cycle-per-second signals at a receiver. Parasitic elements are inhibited by being open circuited by digitally controlled switching diodes. Recirculating shift registers are used to inhibit parasitic elements in the circular arrays to produce the required modulation radiation pattern. A common clock is used to step said registers along to produce the desired rotating pattern.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates to an antenna system, and in particular, one which is capable of providing a rotating radiation pattern which can be used with TACAN systems.

Description of the prior art The tactical deployment of navigation equipment has introduced the requirement that system antennas should be readily transportable. Certain navigational systems, such as TACAN have heretofore used mechanically rotated antennas. Mechanically rotated antennas, although simple and reliable, are bulky, heavy and consume relatively large amounts of primary power.

While electronically rotated scanning antennas have recently come into being, in general, they have been large and weighty.

Accordingly, it is an object of this invention to provide an electronic scanning antenna, which can be made small and light.

SUMMARY OF THE INVENTION According to the invention, an antenna system comprises a radiator, a plurality of parasitic elements associated with said radiator, means coupled to each of said parasitic elements for inhibiting the operation thereof and control means for selectively operating said inhibiting means in a predetermined manner.

BRIEF DESCRIPTION OF THE DRAWINGS mee dipole parasitic elements and their associated grounding circuitry.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a first embodiment, as illustrated in FIG. 1, a central radiator 1, mounted on a counterpoise 4 is surrounded by two concentric rings, 2 and 3, of closely spaced parasitic monopole elements.

Each parasitic monopole element 5, is illustrated in FIG. 2 is coupled to the counterpoise 4 via a diode 8. A switching signal is applied to the diode via an R.F. isolating inductor 7. The switching signal controls the R.F. impedance between the parasitic monopole element 5 and the counterpoise 4 such as to be either an R.F. open circuit or effectively a short circuit to ground.

When an R.F. signal is applied to the monopole radiator 1 it radiates a signal which is modified by the parasitic elements 2 and 3, located as shown in FIG. 1, to produce a desired field pattern. The desired field pattern can be effectively created 0r modified by grounding selected parasitic elements.

A TACAN radiation pattern is a composite pattern comprising a single lobe of cardioid pattern, upon which is superimposed nine secondary variations or ripples. In the presently discussed antenna, selected parasitic elements in the innermost ring 2 are grounded to produce a cardioid field pattern and selected parasitic elements in the outermost ring 3 are grounded to produce the secondary variations in the desired field pattern.

With an appropriate static radiation pattern produced, as above described, it is possible to rotate the pattern by progressively grounding the parasitic elements around the array. This is accomplished as is schematically illustrated in FIG. l by coupling a master clock 11 to two programmed recirculating shift registers, the first of which has its separate bits coupled to the innermost ring of parasitic elements 2 and the second of which has its separate bits coupled to the outermost ring of parasitic elements 3.

The effective radiation pattern depends, for a given radiating frequency, upon the diameters of the concentric rings of parasitic elements. In a second embodiment, as illustrated in FIG. 3, in order to obtain an antenna operative over two frequency bands four concentric rings, two inner and two outer, are used. Rings 15 and 17 may be kept inoperative by appropriate switching circuits while rings 14 and 16 provide a rotating pattern or rings 15 and 17 can provide a pattern while rings 14 and 16 are inactive.

Up to this point, only parasitic monopole elements have been discussed, however, in a third embodiment, parasitic dipoles as shown in FIG. 4 are used to create the radiation pattern. In said embodiment dipole halves 18 are coupled to and separated by a diode 19 one end of which is D.C. coupled to ground via an R.F. choke coil 21 and the other end of which is coupled to a switching signal via R.F. choke coil 20. The switching signal causes the diode 19 to be either an R.F. open or R.F. short and thereby controls the radiation characteristics of the dipole halves.

In a fourth embodiment, as shown in FIG. 5, a stacking technique is used instead of a single parasitic element to obtain an improvement in vertical directivity. In this arrangement parasitic dipoles 24, 25, 26 are stacked one upon another, and are separately coupled to bi-lar R.F. chokes 22, 23 which provide a DC path for control switching signals.

We claim:

1. An antenna system for providing a rotating radiation pattern, comprising:

a central radiator;

a first plurality of parasitic elements associated with 3 4 said radiator positioned to form a first concentric inductor grounded at one end, a plurality of diodes couarray around said radiator; pled to spaced points on said rst and second inductors, a second plurality of parasitic elements associated with said parasitic elements comprising dipole halves coupled said radiator positioned to form a second concentric to each of said diodes, and a control voltage source conarray; nected to one end of said rst inductor. means coupled to each of said parasitic elements of said 5 first and second arrays for inhibiting the operation References Cited a heeof; t Ol C0 l d to ,d rst a v UNITED STATES PATENTS rs con r means up e sai arr y 1a 1,860,123 5/1932 Yagi 343-837X means to produce a' rotatlng lobe pat Herzog a second control means coupled to said second array 3109175 10/1963 Lloyd 343-8335( via said inhibiting means for superimposing minor p 3136996 6/1964 Parker 343`106 lobes on said rotating lobe pattern. 3339205 8/1967 Smltka 343-701 2. An antenna system according7 to claim 1 wherein 15 3375519 3/1968 Burnham 343"100 said inhibiting means comprises a switching diode cou led from the parasitic element to ground, an R.F. chokeland RODNEY D' BENNETT JR Prlmary Examiner a voltage source coupled via said R.F. choke to bias said R. E. BERGER, Assistant Examiner diode on and off.

3. An antenna System according to claim 1 wherein 20 U.S. C1. X.R. said inhibiting means comprises a rst inductor, a Second 343-100, 833, 837 

